1. Field of the Invention
The present invention relates to cable that may be used to transmit signals that may be used to implement two fibre channel (FC) arbitrated loops.
2. Brief Description of Related Prior Art
Network computer systems generally include a plurality of geographically separated or distributed computer nodes that are configured to communicate with each other via, and are interconnected by, one or more network communications media. One conventional type of network computer system includes a network storage subsystem that is configured to provide a centralized location in the network at which to store, and from which to retrieve data. Advantageously, by using such a storage subsystem in the network, many of the network""s data storage management and control functions may be centralized at the subsystem, instead of being distributed among the network nodes.
One type of conventional network storage subsystem, manufactured and sold by the Assignee of the subject application (hereinafter xe2x80x9cAssigneexe2x80x9d) under the tradename Symmetrix(trademark) (hereinafter referred to as the xe2x80x9cAssignee""s conventional storage systemxe2x80x9d), includes a plurality of disk mass storage devices (e.g., disk drives) configured as one or more redundant arrays of independent (or inexpensive) disks (RAID). The disk devices are controlled by disk controllers (commonly referred to as xe2x80x9cback-endxe2x80x9d input/output (I/O) controllers/directors) that may communicate (i.e., exchange data and commands) with the disk devices via Small Computer System Interface (SCSI) protocol communication channels. The disk controllers are coupled via a bus system to a shared cache memory resource in the subsystem. The cache memory resource is also coupled via the bus system to a plurality of host controllers (commonly referred to as xe2x80x9cfront-endxe2x80x9d I/O controllers/directors). The disk controllers are coupled to respective disk adapters that, among other things, interface the disk controllers to the disk devices. Similarly, the host controllers are coupled to respective host channel adapters that, among other things, interface the host controllers via channel I/O ports to the network communications channels (e.g., SCSI, Enterprise Systems Connection (ESCON), or FC based communications channels) that couple the storage subsystem to computer nodes in the computer network external to the subsystem (commonly termed xe2x80x9chostxe2x80x9d computer nodes or xe2x80x9chostsxe2x80x9d).
In the Assignee""s conventional storage system, the disk devices are grouped together into respective sets, and each set of disk devices may be controlled by a respective pair of disk controllers. If one of the disk controllers in the respective pair fails, the other (i.e., redundant) disk controller in the pair may assume the duties of the failed disk controller, and thereby permit the set of disk devices to continue to operate, despite the failure of the failed disk controller.
Also in the Assignee""s conventional storage system, the disk devices are placed in respective housings and stored in one or more chassis. The chassis may include a multiplicity of sets of slots for receiving respective housings within which the respective disk devices are placed. The chassis may also include an electrical back plane having a multiplicity of electromechanical connectors. The connectors may be mated with respective electromechanical connectors of the housings to electrically and mechanically couple the disk devices to the chassis.
It has been proposed to replace with FC protocol communication channels the SCSI communication channels that permit communication among the disk devices and disk controllers in the Assignee""s conventional data storage system, in order to increase the speed with which such communication may be performed. According to this proposal, the FC communication channels may comprise respective serial, unidirectional, FC communication rings or loops.
Each of these FC communication rings or loops may physically take the form of a respective plurality of cables that may couple a respective external I/O port of a respective one of the disk adapters to a respective set of disk devices. For example, in each such FC loop, FC data signals may be exchanged among a respective external I/O port of a respective disk adapter and a respective set of disk devices via one respective conventional electrical cable, and control signals associated with the loop may be exchanged among this external I/O port and set of disk devices via a different respective conventional electrical cable. Alternatively, in each such FC loop, the FC data signals and the control signals associated with the loop may be exchanged among the respective external I/O port of the respective disk adapter and the respective set of disk devices via a single respective conventional cable.
In the Assignee""s conventional data storage system, each of the disk adapters may comprise a plurality of external I/O ports that may be coupled via respective FC loops to respective sets of disk devices. Thus, in the proposed arrangement described above, it may be necessary to use a relatively large number of conventional electrical cables to physically connect all of external I/O ports of the disk adapters to respective sets of disk devices, and it may also be necessary to use different types of cables (i.e., respective sets of cables for transmitting FC data and associated control signals). This is unfortunate, since, among other things, it increases the complexity of cabling connections that must be made among the disk adapters and disk devices, may result in an undesirably large amount of physical space being consumed by such connections, and may result in an undesirably large amount of time and effort being expended by human operators to properly install and manage such cables. Accordingly, it would be desirable to provide means to provide FC communication channels among the disk adapters and disk devices, wherein the number and complexity of cables required to implement such FC communication channels may be reduced compared to the afore-described proposed conventional arrangements.
In accordance with the present invention, an FC cable is provided that may be used in a network data storage system to overcome the aforesaid and other disadvantages of the prior art. In a first embodiment of the FC cable of the present invention, the cable may be used to transmit signals that may be used to implement both a first FC AL and a second FC AL that is distinct from the first FC AL; these FC arbitrated loops may provide FC communication channels among I/O ports of a disk adapter and sets of disk mass storage devices in a network data storage system. The cable of this embodiment may include first set of electrical conductors that may be used to transmit control signals associated with the first FC AL and the second FC AL, and a second set of electrical conductors that may be used to transmit the first and second FC arbitrated loops"" respective data signals.
The first set of electrical conductors may be disposed outside of a periphery of a central region in the cable that contains the second set of electrical conductors. The second set of electrical conductors may comprise first and second subsets of electrical conductors. Each of the first and second subsets of electrical conductors may include two respective pairs of electrical conductors. The first subset of electrical conductors may be for transmitting the first FC AL""s data signals, and the second subset of electrical conductors may be for transmitting the second FC AL""s data signals. The first subset of electrical conductors may be disposed about a first central filler member, and may be surrounded by a first electrical shield member. The second subset of electrical conductors may be disposed about a second central filler member, and may be surrounded by a second electrical shield member.
The FC cable of the first embodiment may further comprise third and fourth electrical shield members. The third electrical shield member may surround the first set of electrical conductors, and the fourth electrical shield member may surround the third electrical shield member.
In the first embodiment of the present invention, each respective electrical conductor in the first and second sets of electrical conductors may comprise a respective metal core surrounded by an insulating material. Further, the central region in the cable of this embodiment may contain two additional filler members, and may be enclosed by a binding member. The cable of this embodiment may further comprise a foil shield member that surrounds the first set of electrical conductors, and a braided shield member that surrounds the foil shield member.
In an FC cable made according to a second embodiment of the present invention, the cable may be used to transmit signals that may be used to implement both a first FC AL and a second FC AL; these FC arbitrated loops may provide FC communication channels among I/O ports of a disk adapter and sets of disk mass storage devices in a network data storage system. The FC cable of the second embodiment of the present invention may comprise a first set of electrical conductors that may be used to transmit respective control signals associated with the first FC AL and the second FC AL, and a second set of electrical conductors that may be used to transmit respective data signals of the first FC AL and the second FC AL.
In the cable of the second embodiment of the present invention, the first set of electrical conductors may be disposed around a central region in the cable, which central region may contain the second set of electrical conductors. The second set of electrical conductors may comprise first, second, third and fourth subsets of electrical conductors. Each of these subsets of electrical conductors may include a respective pair of electrical conductors that may transmit a respective subset of the first and second FC arbitrated loops"" data signals.
Also in the cable of the second embodiment of the present invention, the subsets of electrical conductors may be disposed about a central filler member that is disposed at a central portion of the cable. Each of the subsets of electrical conductors may be surrounded by a respective electrical shield member. The cable of the second embodiment may further comprise a foil shield member that surrounds the first set of electrical conductors, and braided shield member that surrounds the foil shield member.
Additionally in the cable of the second embodiment of the present invention, each respective electrical conductor in the first and second sets of electrical conductors may comprise a respective metal core surrounded by an insulating material, and the central region may be enclosed by a binding member. Also, the cable of the second embodiment of the present invention may further comprise a foil shield member that surrounds the first set of electrical conductors, and a braided shield member that surrounds the foil shield member.
Thus, in summary, each of the FC cables made according to the first and second embodiments of the present invention may include electrical conductors that may be used to transmit the signals (i.e., FC data and associated control signals) that are necessary to implement two respective FC arbitrated loops. When cables made according to these embodiments of the present invention are used to implement FC communication channels among disk adapter I/O ports and disk mass storage devices in a network data storage system, the number of such cables that may be needed to implement such channels may be fewer than the number of cables that may be required to implement such channels according to the above-described proposed conventional arrangements. Additionally, when cables made according to these embodiments of the present invention are used to implement FC communication channels among disk adapter I/O ports and disk mass storage devices in such a network data storage system, only the cables made according to said embodiments may need to be coupled to the disk adapter I/O ports. Advantageously, these features of these embodiments of the present invention may permit the number and complexity of cabling connections that must be made among the disk adapters and disk devices to implement FC communication channels among the disk adapters and disk devices to be reduced compared to the afore-described proposed conventional arrangements.
These and other features and advantages of the present invention will become apparent as the following Detailed Description proceeds and upon reference to the Figures of the Drawings, in which like numerals depict like parts, and wherein: